Android ProgressBar示例

我们可以显示 Android进度条 对话框来显示正在进行的工作的状态，例如下载文件，分析工作状态等。

在这个例子中，我们为虚拟文件下载操作显示进度对话框。

在这里，我们使用 android.app.ProgressDialog 类来显示进度条。Android ProgressDialog是AlertDialog类的子类。

ProgressDialog 类提供了一些方法来处理进度条，如setProgress()，setMessage()，setProgressStyle()，setMax()，show()等。进度对话框的进度范围是0到10000。

让我们看一个简单的例子，在Android中显示进度条。

ProgressDialog progressBar = new ProgressDialog(this);
progressBar.setCancelable(true);//you can cancel it by pressing back button
progressBar.setMessage("File downloading ...");
progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressBar.setProgress(0);//initially progress is 0
progressBar.setMax(100);//sets the maximum value 100
progressBar.show();//displays the progress bar

Android进度条示例，使用ProgressDialog

让我们看一个使用ProgressDialog类创建进度条的简单示例。

activity_main.xml

从工具箱中拖动一个按钮，现在activity_main.xml文件看起来是这样的：

<RelativeLayout xmlns:androclass="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="116dp"
        android:text="download file" />

</RelativeLayout>

Activity类

让我们编写代码来显示进度条对话框。

package example.javatpoint.com.progressbar;

import android.app.ProgressDialog;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
    Button btnStartProgress;
    ProgressDialog progressBar;
    private int progressBarStatus = 0;
    private Handler progressBarHandler = new Handler();
    private long fileSize = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        addListenerOnButtonClick();
    }
    public void addListenerOnButtonClick() {
        btnStartProgress = findViewById(R.id.button);
        btnStartProgress.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View v) {
                // creating progress bar dialog
                progressBar = new ProgressDialog(v.getContext());
                progressBar.setCancelable(true);
                progressBar.setMessage("File downloading ...");
                progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
                progressBar.setProgress(0);
                progressBar.setMax(100);
                progressBar.show();
                //reset progress bar and filesize status
                progressBarStatus = 0;
                fileSize = 0;

                new Thread(new Runnable() {
                    public void run() {
                        while (progressBarStatus < 100) {
                            // performing operation
                            progressBarStatus = doOperation();
                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            // Updating the progress bar
                            progressBarHandler.post(new Runnable() {
                                public void run() {
                                    progressBar.setProgress(progressBarStatus);
                                }
                            });
                        }
                        // performing operation if file is downloaded,
                        if (progressBarStatus >= 100) {
                            // sleeping for 1 second after operation completed
                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            // close the progress bar dialog
                            progressBar.dismiss();
                        }
                    }
                }).start();
            }//end of onClick method
        });
    }
    // checking how much file is downloaded and updating the filesize
    public int doOperation() {
        //The range of ProgressDialog starts from 0 to 10000
        while (fileSize <= 10000) {
            fileSize++;
            if (fileSize == 1000) {
                return 10;
            } else if (fileSize == 2000) {
                return 20;
            } else if (fileSize == 3000) {
                return 30;
            } else if (fileSize == 4000) {
                return 40; // you can add more else if 
            } 
         /* else {
                return 100;
            }*/
        }//end of while
            return 100;
    }//end of doOperation
}

输出：